Method of manufacturing a shaft with surfaces thereof modified

ABSTRACT

A method of manufacturing a shaft having modified surfaces. The method comprises forming thread grooves on surfaces of a cylindrical-shaped base material for a shaft, continuously winding a length of wire in and along the thread grooves, and compressing a peripheral surface of the base material for the shaft with the length of wire wound and received in the thread grooves, in a direction of diameter reduction to perform plastic deformation of crests of thread ridges between the adjacent thread grooves or the crests and the wire to have the length of wire being fixed to and united with the base material for the shaft. The method improves the hardness of surfaces of a base material for a shaft in a relatively simple manner, and transforms properties of surfaces of the base material for a shaft to make the base material for the shaft applicable to other uses.

TECHNICAL FIELD

The present invention relates to a method of manufacturing a shaft withsurfaces thereof modified, and more particularly to a method ofmanufacturing a shaft having a wire, which is formed of a differentmaterial from that of the shaft, fixed to and united with regions belowthe surface of the shaft.

BACKGROUND ART

A technology for preventing damage or abrasion on surfaces of a metallicmaterial is classified roughly into the surface transformation methodand the surface coating method.

The former technology includes a method of forming an alloy layer onsurfaces, such as the cementation method, the nitriding method, themetallic cementation and the like, or quench hardening by heating, amethod making use of residual stress, or the shot peening method. Thesemethods involve complicated and large apparatuses therefor, and areinapplicable or difficult to be applicable to a base material for ashaft, which is composed of a soft metal such as aluminum or the like.

In contrast, the latter technology includes a metal plating methodtypified by hard chromium plating, the metalizing method, the ceramiccoating method, which uses ceramics such as cermet, but involves adisadvantage in poor durability due to a difficult point in its bondingstrength for a base material for the shaft, which is composed of a softmaterial such as aluminum or the like, as well as relatively lowproductivity.

Also, as a surface treatment method for an aluminum alloy, a method isknown which comprises applying the electrochemical treatment (anodicoxidation method) on surfaces of the alloy to form a protective filmcomposed of aluminum oxides and having a thickness of several to severaltens microns to enhance its surface hardness. However, such protectivefilm is small in thickness to be liable to wear, and has less chemicalresistance to be liable particularly to erosion by alkali. In addition,there is caused a problem in cost because it takes considerable time toform such protective film.

Further, the above-mentioned various methods apply to metals as the basematerial, and are not very applicable to synthetic resin materials.

SUMMARY OF INVENTION

The present invention solves the problems of the prior art, and has asits object to provide a method of manufacturing a shaft with surfacesthereof modified; the method serving to improve the hardness of surfacesof a base material for a shaft in a relatively simple manner, andtransforming properties of surfaces of the base material for a shaft tomake the base material for a shaft applicable to other uses.

The present invention provides a method of manufacturing a shaft withsurfaces thereof modified, comprising the steps of: forming a threadgroove on surfaces of a cylindrical-shaped base material for a shaft;continuously winding a length of wire in and along the thread groove;and followed by compressing a peripheral surface of the base materialfor the shaft with the length of wire wound and received in the threadgroove, in a direction of diameter reduction to perform plasticdeformation of crests of thread ridges between the adjacent threadgrooves or the crests and the wire to have the length of wire fixed toand united with the base material for the shaft.

Preferably, a rolling method is used to form the thread groove and tohave the length of wire fixed to and united with the base materials forthe shaft.

In addition, a preferable combination of materials in practicing theinvention can include:

(1) A. base material for a shaft: aluminum or aluminum alloy

B. wire: metallic wire having a greater hardness than that of the basematerial for a shaft

(2) A. base material for a shaft: structural plastics

B. wire: metallic wire having a good conductivity

Of course, other combinations than the above ones are possible inpracticing the invention. The reason for this is that optimumcombinations change depending upon the use of the shafts.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1(A), 1(B), 1(C) and 1(D) are elevational views which illustraterespective steps of the invention, in each of which a base material fora shaft is processed to change the external shape thereof.

FIG. 2 is a cross sectional view of an essential portion of a shaft,which is finally obtained in the invention, and of which surfaces aremodified.

FIG. 3 is an enlarged, cross sectional view of an essential portionillustrating an engaging relationship between thread grooves and a wirein the “thread groove forming step” in the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention will be described in detail with reference to thedrawings, in which an embodiment of the invention is shown.

FIGS. 1(A), 1(B), 1(C) and 1(D) illustrate respective steps of theinvention in terms of changes in the external shape of a base materialfor a shaft which is a member being worked. Further, it should be notedthat a size of the base material for the shaft, which is a member beingworked, is not an actual size because an understanding of the processingsteps is preferential.

FIG. 1(A) shows a cylindrical-shaped base material for a shaft prior toprocessing. FIG. 1(B) shows the base material for a shaft going througha step (hereinafter, referred to as the “thread groove forming step”),in which a thread groove is formed on surfaces of the base material forthe shaft. FIG. 1(C) shows the base material for the shaft going througha step (hereinafter, referred to as the “wire applying step”), in whicha length of wire is wound along the thread groove. FIG. 1(D) shows thebase material for the shaft going through a step (hereinafter, referredto as the “wire fixing step”), in which surfaces of the base materialfor the shaft are compressed to have the length of wire fixed to andunited with the base material for the shaft.

First, a columnar-shaped base material for the shaft (10) having asubstantially smooth surface (10 a) is prepared. Here the base materialfor the shaft is prepared by cutting a coiled wire rod to a desiredlength or cold pressing a metallic material into a columnar-shaped shafthaving a smooth surface.

Subsequently, the base material for the shaft thus prepared is made toundergo the “thread groove forming step”. In this step, a thread groove(11) is spirally formed on a surface of the base material for the shaft.While a rolling method is preferable in terms of work efficiency as amethod of forming the thread groove, other threading methods may beemployed, of course. In addition, the thread groove is U-shaped inprinciple taking into account its matching with a configuration of awire wound and received therein, but may be substantially V-shaped likeconventional threads as the case may be. Also, because the wire (12) inthe subsequent step is wound and received in the thread groove withoutslacking, a width (W) of the thread groove is made to be somewhatgreater than a diameter [d] of the wire, and a depth [D] of the threadgroove is made to assume 1.2 to 1.8, particularly preferably 1.4 to 1.6in terms of D/d. A pitch [p] of the thread groove may be appropriatelyselected taking into account a force, by which the wire is held on theshaft, and a desired abrasion resistance of the shaft surfaces inaccordance with use of and size of the shaft and materials for the shaftand wire.

An example of these data is given below (see FIG. 3). In addition, amaterial for the shaft is A 2017, and a material for the wire is copperwire.

(1) Depth [D] of the thread groove: 1.35 mm

(2) Width [W] of the thread groove: 1.0 mm

(3) Pitch [p] of the thread groove: 2.0 mm

(4) Diameter [d] of the wire: 0.9 mm

(5) Outer diameter of the base material for the shaft: 11.7 mm

Then the base material for the shaft, of which surface is formed withthe thread groove, is made to undergo the “wire applying step”. Here thewire (12) is wound and received in the thread groove (11). A way ofpracticing such step may be manually carried out on the base materialfor the shaft, which is fixed by a fixing device such as a vice or thelike and of which surface is formed with a thread groove, while exertinga predetermined pulling force on one end of the wire, the other end ofwhich is secured to a starting end of the thread groove by means of somemeasures, and exertion of the pulling force on the one end of the wiremay be carried out by means of a tool and a machine. Whether eithermeasures may be employed, it is important to wind the wire in the threadgroove without slacking.

Finally, the base material for the shaft with the wire applied in thethread groove is made to undergo the “wire fixing step”. Here crests ofthread ridges between the adjacent thread grooves (in the case where adiameter of the wire (12) wound and received in the thread groove issmaller than a depth of the thread groove) or the crests and the wire(in the case where a diameter of the wire is larger than a depth of thethread groove) are compressed toward a center of the base material forthe shaft. Concretely, the wire fixing step is carried out byinterposing the base material for the shaft having undergone the “wireapplying step” between a stationary die and a movable die with an axisof the base material for the shaft made in parallel to facing surfacesof the both dies, and rolling the movable die over the stationary diewhile pressing the movable die against the stationary die. As a result,the thread ridges and the wire are subjected to plastic deformation, sothat the wire is embedded spirally in the vicinity of the surfaces ofthe base material for the shaft to be fixed thereto. In the case wherean object being compressed consists of only the crests of the threadridges (see FIG. 3), the wire is made to be embedded completely belowthe surfaces of the base material for the shaft. In contrast, in thecase where an object being compressed consists of both the crests of thethread ridges and the wire, a portion of the wire is made to besubstantially flush with the crests of the thread ridges (a state shownin FIG. 2). Whether either of the states should be selected may beappropriately determined depending upon that purpose, for which the basematerial for the shaft with the wire fixed thereto is used. Of course,the dies must be used which are formed of a material, such as SKD11(alloy tool steels-cold metallic mold, having a greater hardness thanthat of the base material for the shaft.

With the shaft (1) manufactured in the above manner, a major part of thewire (12) or the entire wire in some cases is spirally embedded andfixed at equal pitch, so that the wire is prevented from simplyseparating or falling off whereby the surface modifying effect can bepreserved over a long term.

Incidentally, the respective steps described above are the minimum stepsrequired for practicing the invention, and don't exclude appropriateaddition of necessary steps such as the wire cleaning treatment, surfacetreatment and other steps at necessary points of time.

In this manner, the shaft (1) provided according to the invention can bepreferably used in, for example, valve discs for slide valves and needlevalves, wear resisting machine parts such as various sliding shaftbodies or their base materials.

A combination of the base material for the shaft (10) and the wire (12)in use for such wear resisting machine parts or their base materials ispreferable in terms of durability when using a metallic shaft ofaluminum or aluminum alloy, which is good in workability as the basematerial for the shaft, and a metallic wire, for example, stainlesssteel, spring copper alloy and the like, which is high in hardness andstainless.

The invention can be applied to other purposes than the above-mentionedimprovement of surface hardness of the shaft (1). For example, ifstructural plastics such as polyacetal resin, polyamide resin and thelike is used for the base material for the shaft and a wire rodmaterial, such as copper or a copper alloy, having a good electricalconductivity is used for the wire, the electricity charge heating effectof the wire thus fixed can be used in addition to modification of thesurface hardness of the shaft. Because the shaft obtained in this mannerincludes an electric conductor uniformly distributed in the vicinity ofthe surface thereof, the entire shaft can be uniformly heated, and thusis made applicable as shafts intended for special uses, for example,heating apparatuses, parts for freeze proofing and the like byseparately providing for a heat regulating mechanism such as athermostat and the like.

In addition, in use with the prime object on the electricity chargingeffect of the wire, it goes without saying that, since the use ofstructural plastics for the base material for the shaft is based on theusefulness of lightweight and insulating substances, a material for thebase material for the shaft is not limited to structural plastics.

Industrial Applicability

As described above, according to the invention, the wire applied to thesurface of the base material for the shaft will not simply separate orfall off, and the wire is uniformly distributed in the vicinity of thesurface of the base material for the shaft, so that wear resistingmachine parts or base materials therefor, which are excellent indurability, can be presented at low cost.

Also, shafts, such as heating bodies, having new avenues of use, whichhave not been existent heretofore, can be provided by forming the wirefrom a material which is excellent in electric conductivity.

Accordingly, the invention is of exceedingly great industrial value inproviding a method of manufacturing a shaft with surfaces thereof beingmodified, by which method problems of the prior art are solved, andfurthermore in providing a method of manufacturing a shaft having newavenues of use.

What is claimed is:
 1. A method of manufacturing a shaft having modifiedsurfaces, comprising: forming a plurality of thread grooves withrespective crests of thread ridges on an outer surface of acylindrical-shaped base material for a shaft; continuously winding alength of wire in and along the thread grooves; and compressing aperipheral surface of the base material for the shaft with the length ofwire wound and received in the thread grooves by a rolling method, in adirection of diameter reduction to perform plastic deformation of thecrests of the thread ridges between two adjacent thread grooves or thecrests and the wire such that the length of wire is fixed to and unitedwith the base material for the shaft to form a fixed and united wirewhose outer surface is substantially flush with the surface of theshaft.
 2. The method according to claim 1, wherein a rolling method isused to form said thread groove.
 3. The method according to claim 2,wherein said base material for the shaft comprises aluminum or analuminum alloy; and said wire comprises a metallic wire having a greaterhardness than that of the base material for the shaft.
 4. The methodaccording to claim 2, wherein said base material for the shaft comprisesa structural plastic; and said wire comprises a metallic wire having agood electrical conductivity.
 5. The method according to claim 1,wherein said base material for the shaft comprises aluminum or analuminum alloy; and said wire comprises a metallic wire having a greaterhardness than that of the base material for the shaft.
 6. The methodaccording to claim 1, wherein said base material for the shaft comprisesa structural plastic; and said wire comprises a metallic wire having agood electrical conductivity.
 7. The method according to claim 6,wherein the structural plastic is selected from the group consisting ofa polyacetal resin and a polyamide resin.
 8. The method according toclaim 1, wherein the thread grooves are U-shaped or V-shaped.
 9. Themethod according to claim 8, wherein the thread grooves have a widththat is greater than the diameter of the wire; and a ratio of the depthof the thread grooves to the diameter of the wire is 1.2 to 1.8.
 10. Themethod according to claim 9, wherein the ratio of the depth of thethread grooves to the diameter of the wire is 1.4 to 1.6.
 11. The methodaccording to claim 10, wherein the wire is made of stainless steel or aspring copper alloy.
 12. A method of manufacturing a shaft havingmodified surfaces comprising: forming a plurality of thread grooves withrespective crests of thread ridges on an outer surface of acylindrical-shaped base material for a shaft; continuously winding alength of wire in and along the thread grooves; and compressing aperipheral surface of the base material for the shaft with the length ofwire wound and received in the thread grooves by a rolling method, in adirection of diameter reduction to perform plastic deformation of thecrests of the thread ridges between two adjacent thread grooves or thecrests and the wire such that the length of wire is fixed to and unitedwith the base material for the shaft to form a fixed and united wirewhose outer surface is substantially flush with the surface of theshaft, and so that the wire is completely spirally embedded in thevicinity of the surface of the base material for the shaft.
 13. Themethod according to claim 12, wherein a rolling method is used to formsaid thread grooves.
 14. The method according to claim 13, wherein saidbase material for the shaft comprises aluminum or an aluminum alloy; andsaid wire comprises a metallic wire having a greater hardness than thatof the base material for the shaft.
 15. The method according to claim13, wherein said base material for the shaft comprises a structuralplastic; and said wire comprises a metallic wire having a goodelectrical conductivity.
 16. The method according to claim 12, whereinsaid base material for the shaft comprises aluminum or an aluminumalloy; and said wire comprises a metallic wire having a greater hardnessthan that of the base material for the shaft.
 17. The method accordingto claim 12, wherein said base material for the shaft comprises astructural plastic; and said wire comprises a metallic wire having agood electrical conductivity.
 18. The method according to claim 12,wherein the thread grooves are U-shaped or V-shaped.
 19. The methodaccording to claim 18, wherein the thread grooves have a width that isgreater than the diameter of the wire; and a ratio of the depth of thethread grooves to the diameter of the wire is 1.2 to 1.8.
 20. The methodaccording to claim 19, wherein the ratio of the depth of the threadgrooves to the diameter of the wire is 1.4 to 1.6; and the wire is madeof stainless steel or a spring copper alloy.